One of the primary technical challenges associated with the manufacture of optical systems is component alignment of optical devices. In the manufacturing Micro Electro-Mechanical Systems (MEMS) devices, sub-micrometer alignment tolerances are often required.
There are two general classes of alignment strategies for optical components: active and passive. In passive alignment, alignment features are fabricated directly on the components as well as on the substrate to which the components are to be mounted. The components are then mounted and bonded directly to the substrate using the alignment features.
In active alignment, an optical signal is transmitted through the components and detected, sometimes after an initial passive alignment of the components. The alignment is performed manually, based on checking and adjusting the optical components to achieve the desired performance of the system. Accordingly, the process of checking and adjusting optical components requires substantially higher labor costs than passive alignment. The difference in labor costs is further compounded in fabricating MEMS devices because MEMS devices can have hundreds of components that need to be aligned in order for the system to function properly. In such a system, the cost of active alignment could total thousands of times the cost of passive alignment.
Generally, optical system manufacturing seeks to improve the efficiency of which the optical systems can be configured. Passive alignment is essential to any large scale manufacturing of MEMS optical systems because it drastically reduces the necessary labor costs. The availability of passive aligning optical components greatly influences whether it is economically feasible to produce a particular MEMS optical device.